An electrical vehicle is normally accelerated and decelerated by the adhesive force between each wheel and a rail. However, when a driving force larger than the adhesive force is applied at the starting time of the AC electric motor, idle running of wheels occurs. On the other hand, when a braking force larger than the adhesive force is applied at the braking time, slip of the wheels occurs. Therefore, the acceleration/deceleration performance of electrical vehicles has been hitherto enhanced by detecting idle running/slip and reducing occurring torque of the AC electric motor to rapidly induce re-adhesion. For example, according to Patent Document 1, the average speed of the rotational velocities of plural AC electric motors is first calculated, a wheel diameter difference correcting amount of wheels joined to each AC electric motor is calculated on the basis of the ratio between the average speed and the rotational speed of each AC electric motor, and then a reference speed serving as a reference for the re-adhesion control in each control unit is calculated on the basis of the wheel diameter difference correcting amount and the average speed. The idle running of the wheels is detected on the basis of the average speed and the rotational speed of the AC electric motor to be controlled every control unit, and the torque of the AC electric motor is narrowed down in accordance with the difference between the reference speed and the rotational speed of the AC electric motor to be controlled every control unit, thereby performing the idle running re-adhesion control.
Patent Document 1: JP-A-2001-145207 (Page 3, FIG. 1)